1. Field of the Invention
The invention generally relates to a method for obtaining data on the traffic situation in a road network. More specifically, the invention relates to a method for obtaining data for a plurality of vehicles involved in road traffic and equipped with sensory analysis equipment for collecting traffic-relevant sensor data, which comprise at least one variable representing the current speed v(t) of a given vehicle, for wirelessly transmitting to a center at chronological intervals individual reports concerning the current traffic situation in the vicinity of the given vehicle determined on the basis of collected sensor data by a data processing device arranged in the vehicle. Further, the invention relates to an apparatus in a vehicle for compiling and transmitting such individual reports.
2. Discussion of the Prior Art
Determining and describing the traffic situation is an essential task in the field of traffic telematics, among whose goals is to supply drivers with the most current and helpful information possible, so that the drivers can avoid traffic jams, if possible, and switch to less crowded roads, when needed. The use of stationary collection devices (e.g., beacons, induction loops, etc.) installed at roadside for this purpose is known. However, this entails high costs for creating and maintaining the required infrastructure. It is also disadvantageous that such roadside devices, for system-related reasons, have extremely limited local areas of use, so that a huge number of such devices must be installed to determine the traffic situation in a wide area.
Recently, attempts to determine the traffic situation without using permanently installed roadside devices have also become known, in which information is transmitted from the vehicles of a fleet of sampling vehicles to suitable collection points (e.g., traffic control centers). These vehicles form a sort of measurement station involved in traffic ("floating cars"), and transmit relevant data (in particular, the vehicle speed) via mobile wireless communications devices (e.g., mobile phones) to a data collection point for further processing and evaluation. The results of this evaluation can then be sent to a large number of drivers in the form of driving instructions and recommended detours, so that the drivers can make good decisions about the route to take depending on the traffic situation. The results can also be entered into automatic route planning and guidance systems.
One problem of "floating cars" is that the continuous transmission of the current speed of a large number of vehicles places an extraordinarily heavy load on the transmission channels of the communications devices used, and also constitutes a significant cost factor in using a fee-based communications system. For this reason, an attempt is made to transmit compressed data, if possible, rather than individual measurement values, to the center where the traffic information is collected and processed for the end user. For example, the average speed of a given vehicle could be transmitted to the center at chronological intervals. However, this is still very expensive. It would be much more effective if a decision as to whether particular data are of greater or lesser importance to the traffic situation could be made in the vehicle in which suitable sensory analysis equipment carries out the actual data collection, and data transmission could be limited to important data only. In this respect, it would be of great interest, for example, if the transmission could be limited solely to information concerning detected traffic congestion.
In general, regarding systems for obtaining traffic information based on "floating cars," a large number of reports are automatically produced about events that are unusual and therefore significant from the point of view of the "floating cars." These reports must first be checked thoroughly before flowing into traffic services such as route planning, vehicle guidance, traffic planning and traffic processes. Given the sensory analysis equipment in the "floating cars," which, for reasons of cost, is kept as simple as possible, there would inevitably be misidentifications of various types of events based on a mechanical analysis of the collected sensor data. An especially drastic example of this would be mistaking the event "stopping at rest area" for the event "traffic jam" during an automobile trip. In both cases, the sensory analysis equipment would detect a vehicle speed of zero. In view of the large number of reported events in a traffic information system based on "floating cars," the economic feasibility of such a system, if there is a purely manual solution of the problem of checking and, if needed, correcting event reports that reach the center, is questionable from the start.